Reactions of Wild and Albino Mice in Response to Forced Swimming. ∗

Summary

The suggestions in the literature that there are differences in response between strains of domestic and wild animals of the same species, based on supposed differences in psychological and physiological behavior, have not been borne out by the present study. The wild and albino mice utilized in the current study showed no significant differences in swimming time to exhaustion, or colonic temperature at exhaustion. These observations were in direct opposition to those reported comparing wild and domestic rats. There were individual variations in swimming times at all water temperatures despite the utilization of a precise end point for exhaustion. A valuable criterion for exhaustion appeared to be the final colonic temperature as suggested by the relationship between swimming times, water temperature (at least between 20 and 37°C) and colonic temperature. Other factors markedly shorten the duration of swimming at bath temperatures of 15 and 42°C. Group swimming resulted in a 50% decrease in swim time due to factors other than those which induce exhaustion in individually swimming animals. In view of the large individual variations in swimming times, evaluation of various psychological and physiological stresses must utilize the most reliable methods of pinpointing exhaustion and not depend upon such subjective measures as disorientation of the test animal.